The use of printed books and documents (hereinafter referred to as simply “documents”) has obviously been commonplace for many hundreds of years. Various tools and strategies have evolved to try to make more effective use of printed documents. These range from handwritten (or typed) notes on the contents of documents (either on the document itself or in a separate but related document), to highlighting passages in a document deemed to be of greater significance, to manually copying passages from a document (or using a scanning copier, despite the fact that copyrights are often so infringed), to the simple act of including a printed index at the end of a document to facilitate locating information on a specific topic. Many new tools and strategies have been made possible electronic documents that can be accessed in an electronic, searchable format such as a file on a local computer or a web page that can be accessed with a browser.
The relatively recent innovation of providing a searchable electronic copy of a document that can be accessed using a standard personal computer powerfully increases the ease with which the desired contents can be accessed and utilized. When a traditional index is provided in such a context, once an entry is found, a single click of the mouse can take the user directly to the desired entry in the electronic text. Once a relevant entry has been found, its location can be retained as a “bookmark,” filed according to the user's choice, making future access to the location in the electronic document quick and easy.
Unfortunately, these very useful tools cannot be used with the vast resource of printed books and documents. Even though tremendous advantages accrue with access to an electronic version of a document, these are obviously only available when such an electronic version is available (and a computer is available to access the electronic document). Even in those instances where such an electronic version is available, this still does nothing to enhance the actual use of the paper document itself. Furthermore, when newer revisions and updated versions of either the paper or the electronic version of a document become available, the owner of a previous version generally has little recourse but to go and purchase a new, updated copy of the material.
As is well known in the art, by using traditional methods for document processing (such as, for example, a flatbed scanner combined with appropriate computer software for optical character recognition), a user can create an electronic version of a paper document. However, in addition to the fact that such a task is laborious, time-consuming, and generally error-prone, it usually involves infringement of the copyright held by the author of the textbook in question. Further, even when an electronic version of a document is thus created, it is still subject to the limitations mentioned above—a computer is required to make any use of the additional features offered, and no additional utility is provided for the paper document itself. Despite the prevalence of computers, and despite the advantages conveyed by searchable electronic versions of documents, the continued widespread preference for creating and using paper documents is a clear indication of how attractive they remain to the average user. The portability, convenience, ease of viewing, and even the “feel” of paper documents clearly retain a powerful appeal to most individuals.
An approach that enabled users to easily navigate between printed and electronic versions of documents in a highly secure manner would therefore provide significant utility.